-On picking Adon :
Basically everyone in SF1 was in the "pick your favourite" list at first. With Juri and Cody, there was a number of complex characters, but Adon was a character very easy to understand and use, and they felt they needed one like that. And Adon isn't too bad. They don't really know what people think of him, though, lol. But as a classic/cool character, he was well liked by the team.
But he wasn't just decided to be in yet, Adon doesn't have much impact as a character. Ono also wondered if Adon was alright, or if there wasn't someone else who should have more priority than him. But in the end, he was picked because he's easy to use. He has the right feeling of a martial artist, he's not hard to use, and his gameplay is easy to understand. At this point they just wanted him in, it was easy to come up with stuff for him and regulate him with the new system.
They do wonder how well he'll be accepted by the users, though. They liked making him, but he didn't make a big name for himself in the community. He wasn't an early one to make it in the list, and they didn't know if people wanted him in even if he has a lot of good points. But they feel he's great in the trailer.
-What's he like ?
Looked at by someone who's used to standard chars like Ryu & Ken, he has some strangely shaped attacks. On anti-air technique, Rising Jaguar is close enough to Shouryuuken, the same kind of usage, but it's slightly different. Shouryuuken is pure anti-air, hitting anything above at a specific position, but Rising Jaguar puts some pressure on what's in front of you too. But as an anti-air move, it's less secure than the Shouryuuken. In the Zero era, his attacks were given a slightly different orientation, so he played a little differently (from the others).
It's not that you need great finger skills or pure technique to use him, but he's a bit like an inferior imitation.
They had a good look at the motions, what move goes oblique, if you see a Hadouken what will you do and with what timing if you are on the ground, what do you have to do to hit for sure, but since he moves in an oblique way, from where do you have to be to know you will hit, if the move has this orbit will you miss if you don't know it by heart, and so on.
-Compared to Zero :
Zero had a "casual play" feeling ; this is more "stoic". Adon is the type who figures out where he will connect with the opponent on both character's trajectory. It does seem like he would attack relentlessly when looking at him, but actually you need to play cleverly. Characters with a number of techniques need to know which to use in the right situation, and the opponent doesn't know which will come out, but Adon isn't quite that.
-On his movelist :
The base is Zero 3, but he changed depending on the ISM, like the aerial Jaguar kick in X-ISM. So in the end, he has more moves. But it's still simple.
He's simple to understand, but not that simple to win with, like you don't take the time to finish studying him. Unlike other chars, you can't say "at this distance, he'll do this". Adon has to bait the opponent.
He has a number of moves, and each weak-medium-heavy version has a different trajectory, so you can use the weak version on purpose to make the opponent try to counter.
[skip stuff about 2D - 3D transition for movement and facial features]
-On his progress :
Tweaks and fixes take more time than expected since Adon is a difficult fighter ; they have to rework stuff that worked right before but then changed, especially when put together with everyone else.
He's an easy to use characters, but he's not that strong. Comparatively, Guy is for mid-level players, Cody is for advanced players, but Adon is easier to use than Guy.
... Adon is a little more user-friendly (than Guy). He does have more conventional tactics such as "on anti-air, Shouryuu-FADC", and then connecting the ultra, it's possible to coordinate your movements like that. there's a lot of situations where you can lay some damage, he has a bunch of combos, and possibilities to chose which combo to go for depending on the situation.
The staff tweaking him right now say he's fun to use. Appearance and operability are simple, everything on average with nothing uneven ; though they don't know how players will feel about him and react. Anyone from beginners to advanced players should be able to enjoy him.
He may not look like much, but he's a great character, enjoy him plz plz plz you'll know when you touch him.